Didn't see this posted anywhere (and yes, I did a search for "cnet" and "tethering" so sue me if it's been posted) but CNET has posted step-by-step instructions to allow tethering. Seems simple enough, I'll be attempting the process when I get home from work. (apologies to anyone who's posted these same instructions here already, first time I've seen it w/ screen shots and everything) Good luck! http://reviews.cnet.com/8301-19512_7-10265889-233.html
I've done this for my iPhone on 02-UK and you don't need the Pre-Release, but, different formats might vary